Internal-combustion engine



FIG. 1 is a right-front perspective view of an internal-combustion engine showing our new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view thereof; and,

FIG. 6 is a top plan view thereof. 

The ornamental design for; an internal-combustion engine, as shown and described. 